Bleaching products for use in laundering of fabrics conventionally have been sold in the form of powders and liquids. Consumers have thus been required to measure appropriate dosages from containers holding these products each time they wish to bleach a load of laundry. This measuring process has several drawbacks which are perceived by consumers as rendering liquid or powder bleach inconvenient: the liquid or powder products are easy to spill and not simple to measure accurately. Moreover, consumers usually use about the same amount of bleach for each wash; thus, remeasuring the amount they desire repeats a step performed many times before. Bleach compositions have the additional problem that bleach activity is lost over time; this is especially so for chlorine bleaches in an aqueous liquid.
Liquid bleach compositions in several forms are known, e.g. liquids, powders or pastes (U.S. Pat. No. 4,105,573). It has sometimes been deemed desirable to thicken liquid bleaches. Bleach composition thickeners have included clay, alone or combined with certain polymers (U.S. Pat. Nos. 4,116,849 and 4,116,851) as well as with mixtures of detergents (U.S. Pat. No. 4,337,163); cellulose derivatives and colloidal silica (U.S. Pat. No. 4,011,172).
Delivery of bleach to a washer is made somewhat simpler by use of a pouch. Dry particulate bleach has thus been added in water-soluble film packets (U.S. Pat. No. 3,644,260) as well as in porous pouches (U.S. Pat. No. 4,286,016). Indeed, U.S. Pat. Nos. 4,638,907 and 4,659,390 disclose adding several cleaning actives at once, between two layers of polymeric material laminated together, in a product which segregates each active from the others.
Less common than pouch-delivery of bleach has been delivery of dry chlorine bleach particles by water-soluble sheets (U.S. Pat. No. 4,532,063; 4,557,852 and 4,654,395).
There has been little use of non-water soluble sheet delivery systems for bleach. Applicant believes such systems may afford significant benefits over the art.
Yet certain disadvantages arise with single sheet-type laundry articles. Thus, some substrates are weakened and torn apart by washing, leaving unpleasant pieces to be removed from laundry by the consumer. Many substrate materials for carrying the bleach composition are not bleach-stable and thus disintegrate during storage or become unattractive to use. The requirements of mechanical and bleach stability restricts the substrate materials which may be used.
Even if the substrate is bleach stable, the composite bleaching article should retain its pleasant feel and texture during storage. Some articles lose their pleasant feel and become brittle due, it is believed, to adsorption of ambient moisture. The need to impart a lasting hand and resilience to the bleaching articles also affects the substrates, as well as the chemical compositions, which may be used.
There are further difficulties in processing single sheet-type laundry articles. For example, the bleach composition applied to the sheet should preferably be a viscous material which does not tend to run off the substrate. Additionally, aqueous chlorine bleach compositions have insoluble bleach particles which may not be easily suspended. Syneresis in the bleach composition to be applied to the substrate thus may cause uneven bleach doses from sheet to sheet.
Accordingly, it is an object of the present invention to provide a bleaching article in the form of a bleach-carrying substrate which is flexible when handled, and has a pleasant supple feel rather than a wet, greasy or tacky feel.
It is also an object of the present invention to provide an effective bleaching article for use in an automatic washing machine for laundry fabrics.
Another object of the invention is to provide a bleaching article that is simple to manufacture and convenient to store.
It is a further object of the present invention to provide a bleaching article which does not suffer from loss of bleaching activity and does not suffer physical damage in storage or in use. Physical damage includes shredding of the substrate in the wash as well as substantial flaking off of bleaching composition from the substrate surface.
It is yet another object of the invention to provide an aqueous bleach composition which does not suffer from phase separation and may be applied to a flexible substrate.